3" decat exhaust on 03 STI
11 August 2007, 12:34 AM
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3" decat exhaust on 03 STI
Currently all that is fitted to my 2003 STI is the PPP
I have just bought a full 3" decat system from turbo to back.
I will be fitting this next weekend as i wont have much time on my hands due to a new arrival in the family on the 20th-Aug.
Now i'm going to borrow a boost gauge tomorrow to get an idea of what boost the car makes on it current setup. I have been reading some threads referring to STI's encountering boost spike once a decated exhaust is fitted. I hope this doesn't effect me but undoubtedly it will!!
What can be done to stop this boost spike should it occur.? Apparently there is a restrictor in some boost pipe work which can be increase or decreased in size to help get the boost back in check.? Where is it and should the hole be made bigger or smaller. What size is it at the moment?
Will a 3 port boost solenoid solve the problem as a temp fix. A friends wrx is currently very poorly with a bottom end failure so his 3 port could be used for a while. If this is an option what do you do to fit it?
A few threads also refer to a CEL light coming on and make reference to a resistor to fix this. What is this resistor, where does it go and where do i get one.?
These fixes are veiwed as temporary by me as the car will be remapped by Andy Forrest some time in September but as said i wont have allot of time on my hands to play about with it due to the new baby.
All help appreciated
Rob
I have just bought a full 3" decat system from turbo to back.
I will be fitting this next weekend as i wont have much time on my hands due to a new arrival in the family on the 20th-Aug.
Now i'm going to borrow a boost gauge tomorrow to get an idea of what boost the car makes on it current setup. I have been reading some threads referring to STI's encountering boost spike once a decated exhaust is fitted. I hope this doesn't effect me but undoubtedly it will!!
What can be done to stop this boost spike should it occur.? Apparently there is a restrictor in some boost pipe work which can be increase or decreased in size to help get the boost back in check.? Where is it and should the hole be made bigger or smaller. What size is it at the moment?
Will a 3 port boost solenoid solve the problem as a temp fix. A friends wrx is currently very poorly with a bottom end failure so his 3 port could be used for a while. If this is an option what do you do to fit it?
A few threads also refer to a CEL light coming on and make reference to a resistor to fix this. What is this resistor, where does it go and where do i get one.?
These fixes are veiwed as temporary by me as the car will be remapped by Andy Forrest some time in September but as said i wont have allot of time on my hands to play about with it due to the new baby.
All help appreciated
Rob
11 August 2007, 09:00 PM
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One of my friends had a Prodrive version STi a while back, and he de-catt'd + added a Cone Filter without a remap and melted a hole in the top of no.3 piston.
From what i have read here, and from seeing this... i personally wouldnt fit it until you are ready to have it mapped. Its your call... but if you do... dont give it too much stick until its mapped for it at least.
From what i have read here, and from seeing this... i personally wouldnt fit it until you are ready to have it mapped. Its your call... but if you do... dont give it too much stick until its mapped for it at least.
11 August 2007, 09:25 PM
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you can swap the exhaust over but best to drive it easy say to 1bar boost max and to fit the 3 port thats only done at the time of mapping so not as a fix
11 August 2007, 10:15 PM
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I had to fit my old 3" decat prior to go to see bob r. His advice was to stay below 0.5bar of boost until he could work his magic. Be careful doing this without having a mapping session lined up.
11 August 2007, 11:25 PM
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arrgh, i was kind of banking on the PPP map being able to cope with a 3" system considering its supposed to be quite a rich map. I take it thats not the case then eh?
12 August 2007, 12:23 PM
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Rob,
Short answer is no. Fully decatting allows the engine to process way more air than it's fuelled for (even with the safeties of the factory ECU and PPP map) so as stated above, unless you run pretty much off boost, you'll be running the risk of serious engine damage due to the effects of running lean under load. Killing good old No. 3 piston due to it's position at the end of the fuel feed and closeness to the turbo/exhaust pipework being the probable area of destruction.
A full decat really has to be mapped in to safely maximise the engines performance.
Re changing the boost restrictor (found in the boost pressure take off pipe between the turbo exit and solenoid/actuator T piece BTW) to a narrower bore only really causes the signals received for boost control to misread effectively 'fooling' the ECU. Used to be done with older PPP set ups where the GEMS piggyback daughterboard was installed inside the ECU. Again - not a good move as the ECU hasn't been remapped with the new fuel and ignition requirements (the GEMS daughterboard had these onboard and was hard wired into the ECU) so while you might gain a little boost control,reducing spiking and/or oscillation, you'll still risk running lean.
A 3 port boost solenoid can help (again when mapped in) with achieving the boost targets if your existing solenoid and boost control map can't do it. Sometimes the case due to age/mileage/condition that the 2 port isn't up to the job. Later model cars have full 64 point boost control and (as was the case with mine for example) may not need a 3 port solenoid to control boost at all.
Bottom line fella would be to drop Andy F a line. Find out what he recommends based on your setup and what you want to try and achieve. Then get the bit's fitted as close to remap date as is humanly possible - no messing about and minimal risk to your engine.
Cheers,
Stewart.
Short answer is no. Fully decatting allows the engine to process way more air than it's fuelled for (even with the safeties of the factory ECU and PPP map) so as stated above, unless you run pretty much off boost, you'll be running the risk of serious engine damage due to the effects of running lean under load. Killing good old No. 3 piston due to it's position at the end of the fuel feed and closeness to the turbo/exhaust pipework being the probable area of destruction.
A full decat really has to be mapped in to safely maximise the engines performance.
Re changing the boost restrictor (found in the boost pressure take off pipe between the turbo exit and solenoid/actuator T piece BTW) to a narrower bore only really causes the signals received for boost control to misread effectively 'fooling' the ECU. Used to be done with older PPP set ups where the GEMS piggyback daughterboard was installed inside the ECU. Again - not a good move as the ECU hasn't been remapped with the new fuel and ignition requirements (the GEMS daughterboard had these onboard and was hard wired into the ECU) so while you might gain a little boost control,reducing spiking and/or oscillation, you'll still risk running lean.
A 3 port boost solenoid can help (again when mapped in) with achieving the boost targets if your existing solenoid and boost control map can't do it. Sometimes the case due to age/mileage/condition that the 2 port isn't up to the job. Later model cars have full 64 point boost control and (as was the case with mine for example) may not need a 3 port solenoid to control boost at all.
Bottom line fella would be to drop Andy F a line. Find out what he recommends based on your setup and what you want to try and achieve. Then get the bit's fitted as close to remap date as is humanly possible - no messing about and minimal risk to your engine.
Cheers,
Stewart.
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12 August 2007, 04:48 PM
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Rob,
Short answer is no. Fully decatting allows the engine to process way more air than it's fuelled for (even with the safeties of the factory ECU and PPP map) so as stated above, unless you run pretty much off boost, you'll be running the risk of serious engine damage due to the effects of running lean under load. Killing good old No. 3 piston due to it's position at the end of the fuel feed and closeness to the turbo/exhaust pipework being the probable area of destruction.
A full decat really has to be mapped in to safely maximise the engines performance.
Re changing the boost restrictor (found in the boost pressure take off pipe between the turbo exit and solenoid/actuator T piece BTW) to a narrower bore only really causes the signals received for boost control to misread effectively 'fooling' the ECU. Used to be done with older PPP set ups where the GEMS piggyback daughterboard was installed inside the ECU. Again - not a good move as the ECU hasn't been remapped with the new fuel and ignition requirements (the GEMS daughterboard had these onboard and was hard wired into the ECU) so while you might gain a little boost control,reducing spiking and/or oscillation, you'll still risk running lean.
A 3 port boost solenoid can help (again when mapped in) with achieving the boost targets if your existing solenoid and boost control map can't do it. Sometimes the case due to age/mileage/condition that the 2 port isn't up to the job. Later model cars have full 64 point boost control and (as was the case with mine for example) may not need a 3 port solenoid to control boost at all.
Bottom line fella would be to drop Andy F a line. Find out what he recommends based on your setup and what you want to try and achieve. Then get the bit's fitted as close to remap date as is humanly possible - no messing about and minimal risk to your engine.
Cheers,
Stewart.
Short answer is no. Fully decatting allows the engine to process way more air than it's fuelled for (even with the safeties of the factory ECU and PPP map) so as stated above, unless you run pretty much off boost, you'll be running the risk of serious engine damage due to the effects of running lean under load. Killing good old No. 3 piston due to it's position at the end of the fuel feed and closeness to the turbo/exhaust pipework being the probable area of destruction.
A full decat really has to be mapped in to safely maximise the engines performance.
Re changing the boost restrictor (found in the boost pressure take off pipe between the turbo exit and solenoid/actuator T piece BTW) to a narrower bore only really causes the signals received for boost control to misread effectively 'fooling' the ECU. Used to be done with older PPP set ups where the GEMS piggyback daughterboard was installed inside the ECU. Again - not a good move as the ECU hasn't been remapped with the new fuel and ignition requirements (the GEMS daughterboard had these onboard and was hard wired into the ECU) so while you might gain a little boost control,reducing spiking and/or oscillation, you'll still risk running lean.
A 3 port boost solenoid can help (again when mapped in) with achieving the boost targets if your existing solenoid and boost control map can't do it. Sometimes the case due to age/mileage/condition that the 2 port isn't up to the job. Later model cars have full 64 point boost control and (as was the case with mine for example) may not need a 3 port solenoid to control boost at all.
Bottom line fella would be to drop Andy F a line. Find out what he recommends based on your setup and what you want to try and achieve. Then get the bit's fitted as close to remap date as is humanly possible - no messing about and minimal risk to your engine.
Cheers,
Stewart.
Out of interest how can you tell which models have 64 point boost control.?
Rob
13 August 2007, 11:34 AM
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Originally Posted by rob2006
Out of interest how can you tell which models have 64 point boost control.?
My advice would be to ask Andy F - he's working on these cars all the time and will be able to reliably inform you what your model ECU is capable of and whether a 3 port solenoid will be required (by him) to help achieve your mod objectives.
I know that MY05 on cars have this capability as it's specifically what I asked Andy about - afraid I can't sensibly comment on earlier models. Sorry!
(However, interesting for example that Mocom Racing in their £400 Summer Remap Special - see Trader Announcements - specifically mention their mapping is achieved on the OE 2 port solenoid and participants don't require a 3 port for MY00 on)
IMHO best to liaise directly with the man who's going to do the remap as (with much about engine tuning) there are different approaches to achieving the desired results.
Cheers,
Stewart.
13 August 2007, 11:44 AM
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Originally Posted by rob2006
Will a 3" system mate to the PPP downpipe?
The PPP sportscat DP has a 2.5" exit to mate with the pipework on the rest of the system.
Think you'd have to approach Milltek for a true 3" sportscat system as I'm not sure anyone else currently makes such a beast for the Impreza (could well be wrong though - I didn't research too extensively as I wanted to pass roadside checks and the PPP sportscat met my own requirements).
AFAIK with the exception of Milltek, all other 3" systems are turbo back decat 'race - not for use on public highway, ahem officer' designs.
Cheers,
Stewart.
18 August 2007, 07:19 PM
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Fitted the 3" system today and haven't experienced any boost spikes at all. None the less i will keep the loud peddle to a minimum.
Sounds absolutely fantastic.!!
Rob
Sounds absolutely fantastic.!!
Rob
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